Effect of thick SiC interphase layers on microstructure, mechanical and thermal properties of reaction-bonded SiC/SiC composites

Taguchi, Tomitsugu; Igawa, Naoki   ; Yamada, Reiji; Jitsukawa, Shiro

SiC/SiC composites are expected to be one of the candidate materials for fusion reactors because of the low radioactivity after neutron irradiation and excellent mechanical properties at high temperature. Reaction-Bonding (RB) process was employed since this process has a possibility of producing a much denser matrix compared with other processes. SiC fibers, however, adhere strongly to the matrix because of high reactiveness of molten Si with the SiC fiber during RB process. In this study, we investigated the effects of SiC layer as an interphase on fracture behavior in the SiC/SiC. The specimen without an interphase layer showed catastrophic failure behavior while the specimen with SiC interphase layer exhibited non-catastrophic failure behavior by 3-point bending testing. The microstructure observation indicated that SiC fibers did not adhere to the matrix in the specimen with SiC interpahse layer. After 3-point bending testing, the pull-out phenomenon occurred in the SiC/SiC with SiC interphase layer while did not occur in the composite without interphase layer.